A fixed magnetic disk drive has often been used recently as an external recording device for information processing machines such as computers. FIG. 9 shows the basic configuration of a fixed magnetic disk drive, including a non-magnetic metal layer 12 formed on a non-magnetic substrate 11 as a non-magnetic base substance 1, and a non-magnetic metal base layer 2 that is laminated on the base substance 1. A magnetic layer 3 made of cobalt--chromium--tantalum (Co--Cr--Ta) or cobalt--chromium--platinum (Co--Cr--Pt), being a ferromagnetic alloy, is laminated in thin film form on the metal base layer 2, and thereafter an amorphous carbon protective layer 4 is formed on this magnetic layer 3.
Then, a lubrication layer 5 composed of a liquid lubricant is disposed as required on the protective layer 4 to form the magnetic disk.
As the non-magnetic base substance 1, for example, a substance formed with an Ni--P plated layer 12 using an electroless deposition process on a non-magnetic substrate 11 made of Al--Mg alloy, an alumite base substance, a glass base substance, or a ceramic substance, is used. This base substance is ground down as required, or may be formed with irregularities using textures. While this non-magnetic base substance 1 is heated to a temperature of about 200.degree. C., the non-magnetic metal base layer 2 made of Cr, the magnetic layer 3 made of Co--Cr--Ta, and the protective layer 4 made of amorphous carbon are sequentially laminated using a sputtering process in an argon atmosphere. Then a fluorocarbon-based liquid lubricant is coated on the protective layer 4 to form the lubrication layer 5, thereby creating a magnetic disk.
When such a magnetic disk is mounted on a hard disk drive, the disk repeatedly contacts the recording head disposed on this device. When the hard disk drive is shut down, the head is in contact with the surface of the magnetic disk. Meanwhile, when the drive is operating, the head is levitated slightly from the magnetic disk surface, when information is either read or written, and the system adopted is referred to as the contact-start-stop (CSS) system. Therefore, because it is a CSS system, great impact may occur momentarily between protrusions on the head and the magnetic disk surfaces when the power supply is turned on and off, or because of the seeking motion of the head. To protect the magnetic layer from such mechanical shocks, a protective layer is formed on the surface of the magnetic layer, and depending upon the particular, or usage of the disk, a liquid lubricant film is also formed. Generally, in the case of disks with diameters smaller than 5 inches, carbon is used as the material for the protective layer, which is formed using a sputtering process in an argon atmosphere. As a substitute, oxides, such as for example zirconia oxide, can also be used. One of the reasons that carbon has been adopted as the protective layer material is that the amorphous carbon layer formed using a sputtering process has a relatively strong graphite constitution, a characteristic peculiar to graphite, which therefore exhibits a low friction coefficient under an atmosphere containing much moisture.
Such a carbon protective layer has sufficient wear resistance against conventional MnZn ferrite heads (with a Vickers hardness of about 650), and also exhibits good anti-CSS characteristics. However, when compared with hard ceramic materials such as Al.sub.2 O.sub.3. TiC and CaTiO.sub.3 which are used as the slider materials for thin-film heads or MIG heads (with a Vickers hardness of about 2000) that have recently been adopted in fixed magnetic disk drives, such a carbon protective layer as described above is apt to wear down, and depending on the case, it may crush the head. On the other hand, when an oxide-based protective layer with a high degree of hardness is used, it does not wear down so easily, although this raises a problem in that the layer is too hard, and has an excessively high friction coefficient. That is, a momentary head touch with a high energy that occurs during the levitation associated with a seeking motion or a CSS operation due to foreign materials or protrusions on the disk surface can cause the head to be instantaneously crushed. In recent years, a method has been proposed in which a diamond-like carbon film, which has a high hardness diamond constitution and a higher diamond bonding ratio than that of the graphite bonding, is formed on a magnetic layer as a protective layer. This diamond-like carbon film has, in addition to the carbon's excellent sliding characteristics, a high hardness because it is a diamond structure, and therefore, its anti-wear characteristic with respect to a high-hardness Al.sub.2 O.sub.3. TiC slider or CaTiO.sub.3 slider is superior. Several ideas in this area have already been presented. For example, Japanese laid-open patent application 61-12627 discloses a compound layer made of a hard carbon layer and a fluorine-containing lubrication layer formed using a sputtering process under a mixed atmosphere with an inert gas and a hydrocarbon gas, or a CVD process. Laid-open patent application 2-71422 discloses a film carbon layer, in which hydrogen bonds are found by Raman spectral analysis. In addition, laid-open patent application 2-29919 discloses a carbon layer, whose molecular structure is examined by Raman spectral analysis. Furthermore, laid-open patent application 2-87322 discloses a carbon film containing hydrogen and a magnetic recording medium coated with a lubricant, and laid-open patent application 1-258220 discloses that a diamond-like carbon film with a hydrogen content of 2-7.times.10.sup.22 atoms/cc has a hardness equivalent to that of a high-hardness slider, and also has an excellent anti-CSS characteristic as a high-hardness slider protecting layer. Moreover, laid-open patent application 2-282470 discloses that a carbon protective film formed using a sputtering process in a hydrocarbon gas environment has a similar degree of hardness as conventional graphite protective films, in which carbon is formed using a sputtering process in an atmosphere containing only argon, and that its surface is hydrophobic.
The inventors of the present invention have discussed each of the above proposals. However, none of the proposals have provided results that sufficiently satisfy the sliding characteristic requirement against hard sliders made of Al.sub.2 O.sub.3. TiC or CaTiO.sub.3. In carbon protective layers with the above structures, if a high-hardness layer with high diamond bonding, in which the diamond constitution has been increased, is formed, wear resistance against a high slider may be improved. However, if its hardness is too high, a problem is presented in that it can scratch the magnetic head, and its abrasive powder may further damage the magnetic head and the magnetic disk, thereby leading to increased wear. Conversely, if the hardness is too low, the layer will be worn out against the hard slider as it makes contact with the carbon layer. Thus, the above conventional technologies have not yet discovered film materials that possess excellent sliding characteristics and also have a low friction coefficient and wear resistance, and which, at the same time, exhibit optimal anti-CSS characteristics.